Gun-fire control system



March 15, 1960 R. E. CROOKE GUN-FIRE CONTROL SYSTEM Filed Oct. 21,1938

INVENTOR ATTORNEY United States Patent GUN-FIRE CONTROL SYSTEM Raymond E. Crooke, Little Neck, N.Y., assignor to Sperry Rand Corporation, a corporation of Delaware Application October 21, 1938, Serial No. 236,182

3 Claims. (Cl. 235-615) The invention herein disclosed relates to a mechanism for controlling the aiming or setting of ordnance and more particularly to a mechanism especially suitable for controlling the aiming of anti-aircraft guns.

In the art of controlling the setting of a gun such that when fired the shell will hit the target, there are certain factors that must be considered and their values determined to define the position in which the gun must be placed in space, that is, the direction in which it should be aimed. Such factors are, for example, the training of the gun in azimuth, elevation of the gun above the horizontal, fuse setting, etc.

In determining the values of these factors when the gun and the target are moving, consideration must be given to the distance the target moves between the instant the gun is fired and the instant the shell hits the target. The present values of the factors are those values at the instant the gun is fired. As applied to range, the present range is the range at the instant the gun is fired. This present factor must be increased or decreased to determine the advance range, that is, the distance which the shell must travel to reach the target.

Estimated factors are those determined by observations or calculations, such as for example, the range obtained by observations with range finders.

The purpose of gun controlling mechanisms is to indicate the values of the factors of gun setting and maintain those factors correctly in accordance with the relative movement of the target and gun mount. As heretofore constructed, the values representing the present relative position of the target, i.e., the range, bearing and elevation at the time of observation, were set up in the mechanism. The mechanism operated to generate these values in accordance with the relative movement of the target and the gun mount and also computed the advance values, that is, the range, bearing and elevation corrected for the time of flight of the projectile. The factors of the gun setting defining the guns position were then determined from these advanced values. It will thus be seen, three were three steps used heretofore and in the following order: (1) setting up and maintaining in the mechanism the present range, bearing and elevation of the target; (2) the mechanism calculating the advance factors; and (3) the mechanism calculating the gun position values.

The invention herein disclosed has for a purpose and object to provide a mechanism of this type that is much simpler than any heretofore used. This is accomplished in accordance with the invention by providing a mechanism in which the advance values of range, bearing and elevation are directly set up and maintained in the mechanism. These advance values are initially estimated from the observed values of the position and the mechanism operates to generate the advance values and to calculate the present values of range, bearing and elevation. The present values thus obtained are compared with the observed values. Any necessary correction in the advance values are made so that the calculated present values agree with the corresponding observed values under which conditions the advance values as generated are correct.

It will thus be seen, the three steps, heretofore known, are used but in the following order: (1) the estimated advance factors are set up and maintained in the mechanism; and (2) the mechanism calculates the present values of the factors and the gun position values simul' taneously. A particular advantage of applicants invention is that fewer parts, especially auxiliary servo motors, are needed and the mechanism as a whole is simpler in construction. In applicants arrangement the values'of advance position obtained directly from the variable speed or integrator units have sufiicient power to operate the major portion of the mechanism required to calculate the gun position from the advance position of the target as generated in the mechanism and at the same time to operate the mechanism necessary to calculate present values of target position for comparison with observed values. This is a decided advantage in this type of mechanism where the inertia of parts and the power transmitted are factors of accuracy.

A mechanism of this type, embodying the invention, is illustrated diagrammatically in the single figure of the accompanying drawings. In the following description of the illustrated mechanism the nomenclature common to those skilled in the art will be used and the parts of the mechanism utilized in conjunction with any particular value will be designated by the character representing the value together with appropriate numerals to distinguish the several parts.

In general, the instrument illustrated comprises mechanism for initially setting up and maintaining, by integrating or generating, the several advance values of target position, a ballistic computer for determining the necessary factors of setting for the particular gun, calculating mechanism for making the necessary calculations, and indicators for indicating the factors of gun setting and for comparing the corresponding computed present values of target position with the observed values. The mechanism for setting up and maintaining the range is designated generally by the character R; the mechanism for setting up and maintaining the elevation is designated generally by the character A; and the mechanism for setting up and maintaining the relative bearing of the target is designated generally by the character B. The ballistic computer includes mechanism e for determining the superelevation, mechanism T for determining the time of flight of a projectile, and mechanism F for determining the fuse setting. Primarily, the calculating mechanism includes several multipliers and certain differentials. All of the several values are indicated on dials provided for the purpose.

The advance range R 18 initially set up on the mechanism by rotating a handle R3 until a counter R4 indicates the estimated advance range in yards. Rotation of the crank handle R3 affects adjustment of the counter R4 through gears R5 and R6, shaft R7, differential R8, shaft R9 and shaft R10. The crank handle R3 is movable longitudinally of its axis of rotation and upon being pressed inwardly, the gear R5 meshes with a gear R11 as well as the gear R6. The ratio of gears R5 and R11 is such that when engaged, shaft R12 upon which gear R11 is mounted rotates to effect a change in rate dR proportional to the change of the advance range applied. Shaft R12 is connected to the adjustable element or ball carriage R13 of an integrator through a shaft R14, a pinion R15 and a rack R16 secured to the ball carriage R13. The integrator consists of a disk R17 that is rotated at a constant speed by a motor M, balls R18 carried by the ball carriage R13 and a roller R19. The balls R18 frictionally engage the disk and roller and the roller is rotated at a speed proportional to the displacement of the balls from the center of the disk. Thus, through the shaft R12, the ball carriage is adjusted in accordance with the rate of change of the advance range and the output of the integrator represents the integrated change in the advance range. The output roller R19 of the integrator is connected by a shaft R20 to the differential R8. Thus, rotation of the shafts R9 and R10 represents the algebraic sum of the position of the shaft R7 and the integrated change of the advance range from the roller R19, and the counter R4 indicates at all times after the initial setting by the handle R3 the advance range as generated by the integrator.

The center of a differential R21 is rotated in accord ance with the advance range by the shaft R10 which is connected to the center of the differential R21. One side of the differential is connected to a hand crank R22 that is provided for making spot corrections in the advance range. The other side of the differential R21 is connected to a shaft R23 which is also connected to the center of another differential R24. In the differential R24 the product of the rate of change of advance range dR times the time of flight of the projectile T is combined with the advance range to obtain the present range for comparison with the observed range.

As is well known in the art, the time of flight of the projectile is dependent upon the elevation and the range. To obtain the time of flight, a conventional three dimensional cam T1 is used, such as is disclosed and described is represented by the rotational position of cam T1 and is set up in the mechanism by the rotation of shaft R26, which is connected to shaft R10 through shaft R25. The cam arm T6 is internally threaded at its upper edge and engages the threaded portion T3 of shaft A22, which is connected to shaft A10 through shaft A18. As the rotation of shaft A10 represents changes in elevation, the position of the cam follower T6 along the threaded portion T3 of shaft A22 represents elevation. It will thus be seen that the movement of the cam follower T2 about the axis of shaft A22 depends upon the rotation of cam T1 and the particular surface of cam T1 with which cam follower T2 is in contact which is determined by the rotation of shaft T3. To measure this rotation of arm T6, splined shaft T is passed through a block on cam arm T6. On the end of shaft T5 is mounted a sector gear T4 whose arcuate surface has a radius of curvature equal to the distance of the surface from the axis of shaft T3. The arcuate surface of sector gear T4 meshes with gear T7 secured to shaft T8. It will thus be seen that shaft T8 is rotated in proportion to the movement of cam arm T6 about the axis of shaft A22, which is proportional to the rotation of shafts A22 and R26. The surface of cam T1 is designed for the particular characteristics of the ordnance for which the cam is to be used.

The shaft T8 is connected through a shaft T9 to actuate one part of a multiplier TR. The other part of the multiplier TR is actuated in accordance with the rate of change of range (1R2. This is effected through a shaft R27 connected to shaft R12, and shafts R28 and R29, connected together for rotating a pinion R30 meshing with a sector gear on the multiplier TR. The output of the multiplier or the product of a'R times the time of flight is represented by the rotation of a shaft R31 connected to the multiplier and to one side of the differential R24. Rotation of shaft R31 is therefore proportional to the change in advance range during the time of flight T. This change in range is algebraically subtracted from the advance range R, in the differential R24 to obtain a rotation of a shaft R32, connected to the other side of the differential R24, representing the present range.

The shaft R32 is connected to rotate one, R33, of a set of concentric indexed dials in a comparer R34. The other dial R35 in the comparer is rotated by a receiver R36 of self-synchronous transmission systems in accordance with the observed range. The calculated present range is thus compared with the observed range and correction is made in the generated advance range by handle R3 until the calculated present range corresponds to the observed range. By pressing handle R3 inwardly as the correction is made the rate will be simultaneously adjusted. This rate adjustment is comparable to that disclosed and patened in Ford Patent No. 1,468,712.

In like manner the advance elevation A is set up on the instrument and the present elevation determined and compared with the observed elevation. The advance elevation is initially set up on the mechanism by rotating a crank handle A3 that is connected to rotate an indicator A4 through gears A5 and A6, a shaft A7, a differential A8, a shaft A9 and a shaft A10 connected to the indicator A4. The crank handle A3 is shiftable longitudinally of its axis of rotation and when pushed in the gear A5 meshes with a gear A11 as well as with gear A6. The ratio of gears A5 and A11 is such that gear A11 and a shaft A12 to which it is connected are rotated, upon rotation of the crank handle A3, to effect a change in the rate of change of the advance elevation, 11A,. Through a shaft A13, a pinion A14 and a rack A15 rotation of shaft A12 effects movement of the ball carriage of an integrator A16, the output roller of which is connected by a shaft A17 to the differential A8. Thus, the integrated change of elevation is continuously added to the advance elevation initially set up to generate, continuously, and indicate the advance elevation. The shaft A10, the rotation of which represents the advance elevation is connected to a shaft A18 to effect rotation thereof. Shafts A19 and A20 constitute, in effect, a continuation of shaft A18 in that they are respectively connected to shaft A18 and to each other. The shaft A20 is connected to one side of a differential A21 wherein the product of the rate of change of elevation multiplied by the time of flight is subtracted from the advance elevation to obtain the present elevation for comparison with the observed elevation.

The product of the rate of change of elevation and the time of flight is obtained from a multiplier TA. As previously stated the cam follower T2 of the time of flight mechanism T is shifted axially of the cam T1 in accordance with the advance elevation. This is effected through the screw shaft T3 which is connected to shaft A18 through a shaft A22. In the manner heretofore described, the shaft T8, and in consequence the shaft T9, is rotated in accordance with the time of flight of the projectile. The shaft T9 is connected by a shaft T10 to one part of the multiplier TA. The other part of the multiplier is connected through a shaft A23 and associated pinion A24 to a shaft A25 which is connected to shaft A12. Thus, one part of the multiplier is actuated in accordance with the time of flight of the projectile and the other part in accordance with the rate of change of elevation. The product represents the change in elevation over the period of the time of flight. This product is represented by rotation of a shaft A26 that is connected to the multiplier and to one side of a differential A27, the purpose of which differential will hereinafter appear. Through the differential a shaft A28, connected to the other side of the differential and to one side of the dif' ferential A21 is rotated in accordance with the change of elevation during the period of the time of flight, which quantity is also termed the vertical deflection due to movement of the target.

The center of the differential A21 is connected to a shaft A29 which is in consequence rotated in accordance with the diflerence between the generated advance eleva tion and the change of elevation during the time of flight, that is, shaft A29 is rotated in accordance with the present elevation. Shaft A29 drives one, A30, of a set of dials of a comparer A31 and the other dial, A32, is rotated in accordance with the observed elevation by a receiver A33 operated in accordance with the elevation angle of a. sighting device. Thus, correction in the advance elevation, if necessary, may be made so that the calculated present elevation and the observed elevation continuously correspond.

The advance bearing BD of the target in the plane of the deck is initially set into the mechanism by a hand crank B1 which rotates a gear B2 secure thereon and meshing with a gear B3 secured on a shaft B4 that is connected to one side of a differential B5. The center of the differential B5 is connected to one side of another differential B6 by means of which the heading of the ship upon which the gun is mounted, as obtained from the compass, is algebraically added to the true bearing of the target. The compass heading is inserted in the differential through a hand crank B7 connected to the differential but may also be inserted automatically if desired. The center of the differential B6 is connected, through a gear B8 and a shaft B9 to an indicator B10 which indicates the advance relative bearing of the target in the deck.

The advance bearing of the target is continuously generated by an integrator B11, the ball carriage of which is set in accordance with the rate of change of bearing in the plane of the line of sight. This setting of the ball carriage is effected through a shaft B12 having a gear B13 thereon which is positioned to be engaged by gear B2 when the crank handle is pushed inwardly. The ratio of the gears B2 and B13 is taken for the average angle of elevation, and such that the ball carriage of the integrator is set in accordance with the rate of change of advance bearing, dBNg, in the plane of the line of sight. The disk of the integrator B11 is driven by another integrator B14.

The disk of the integrator B14 is driven at a constant speed by the motor M. The ball carriage of the integrator B14 is positioned in accordance with the secant of the advance angle of elevation. This is effected through a secant cam A34 which is a face cam having a cam groove therein that varies in relation to the center of the cam in accordance with the secant of the angle of rotation of the cam. A cam follower in the groove is connected by a rod A35 to the ball carriage of the integrator B14. The cam A34 is rotated in accordance with the advance elevation through a shaft A36 having a pinion A37 thereon meshing with gear teeth on the secant cam. The driven roller of the integrator B14 is thus driven at a speed proportional to the secant of the advance elevation. This roller is connected through shafts B15, B16 and B17 to drive the disk of the integrator B11 and the output of the integrator B11 is the generated change in advance bearing of the target in the plane of the deck. The driven roller of the integrator B11 is connected by a shaft B18 to one side of the differential B5 and thus the generated change in bearing in the plane of the deck is added to the bearing as set in the mechanism through the crank B1. This angular value is also transmitted to the gun mount through a transmitter B19 which is connected to the shaft B9 through shafts B20, B21 and B22.

The shaft B21 is also connected to one side of a differential B23 wherein the horizontal deflection D is algebraically subtracted, as hereinafter described, to obtain the generated relative present bearing. The other side of the differential B23 is connected by shafts B24 and B25 to one dial, B26, of a set of dials in a comparer B27. The other dial B28 of the comparer B27 is connected to a receiver B29 which rotates the dial in accordance with the observed bearing of the target. If the generated relative present bearing does not correspond with the observed bearing proper corrections are made to the advance values so that it does correspond.

The horizontal deflection is obtained by reducing the sight deflection to the horizontal and this factor is algebraically subtracted, in the differential B23, from the advance bearing to obtain the present bearing for comparison with the observed bearing as above described. The sight deflection includes the deflection across the line of sight due to the wind and movement of the ship upon which the gun is mounted, the drift of a shell and the deflection due to movement of the target. To obtain the deflection due to wind and movement of the ship upon which the gun is mounted, the total lateral deflection, that is, the component due to wind and the component due to movement of the ship across the line of sight is multiplied by the advance range. The multiplication of these factors is effected in a multiplier DR. The component due to wind and movement of own ship is obtained from wind and own ship component solvers (not shown) and is represented by the angular movement of a shaft D1 that is connected to operate one side of the multiplier DR. The other side of the multiplier is op erated through a shaft D2 connected to the shaft R10. The output of the multiplier DR, represented by the angular movement of a shaft D3 connected thereto, is thus the deflection due to movement of own ship and the wind across the line of sight.

This quantity is added in the differential D4 to the super elevation as it is well known that the drift of a shell is substantially proportional to the super elevation. The super elevation is therefore added to deflection due to wind and movement of own ship to introduce the drift correction. The super elevation is obtained from a super elevation cam e1 which is rotated in accordance with the advance range R through a shaft e2 connected to the shaft R25. A cam follower e3 is moved along the cam e1 axially thereof by a screw shaft e4 rotated in accordance with the advance elevation through a shaft e5 connected to the screw shaft c4 and the shaft A18. The cam follower moves axially of the cam e1 along a polygonal shaft e6 extending through the arm e7 of the cam follower. A sector gear e8 is mounted on the shaft c6 and movement of the cam follower e3 by virtue of rotation of the cam e1 thus effects rotation of a shaft e9 which is connected to the sector gear 28 through a pinion e10. Rotation of the shaft e9 thus represents the super elevation. The shaft 29 is connected through shafts 211 and e12 to the center of the differential D4 wherein this factor is added as drift to the deflection due to wind and movement of the ship across the line of sight. These combined factors are represented by the rotation of a shaft D5 connected to the other side of the differential D4 and to one side of a differential D6.

In the differential D6 the deflection due to movement of the target is added to obtain the sight deflection. A multiplier DT is provided from which the deflection due to movement of the target across the line of sight is obtained. In the multiplier DT the rate of change of advance bearing in the plane of the sight is multiplied by the time of flight of the projectile. One part of the multiplier is therefore connected to the shaft T9 and another part is connected by a shaft B36 to the shaft B12. The output of the multiplier or the product of these two factors is represented by the angular movement of a shaft D7 connected to the output side of the multiplier and to the center of the differential D6. The other side of the differential D6 and the shaft D8 connected thereto are thus rotated in accordance with the computed sight deflection. The shaft D8 is connected to a shaft D9. A shaft D10 and a shaft D11 are rotated in accordance with the angular movement of shaft D9 by follow-up mechanism designated by the character Dll. The shaft D11 is connected to one side of a differential D12. The center of the differential D12 is connected through a gear D13 and a shaft D14 to a crank handle D15 by means of which spot corrections may be made to the sight deflection. The other side of the differential is connected through shafts D16, D17 and D18 to a transmitter D19 of a self-synchronous motion transmitting system.

The shaft D17 is also connected to rotate a shaft D20 connected to a converter DH in which the deflection in the plane of the line of sight D is converted to the deflection in the horizontal D Such converters are well known in the art and merely divide deflection in the plane amazes of the line of sight by the cosine of the angle of elevation. To accomplish this, there is provided a rotatably mounted cosine cam DHI which is a face cam having a cam groove laid out so that the distance of the groove from the center of the cam represents the cosine of the angle by which the cam is rotated. The cam is rotated in accordance with the angle of advance elevation through a pinion A39 meshing with gear teeth on the periphery of the cam. The pinion A39 is mounted on a shaft A40 connected to shaft A19. A cam follower in the cam groove actuates, through a bar Dl-I2, one part of a divider DH3. The other part of the divider is actuated through a pinion D21 mounted on the shaft D20. A shaft D22 connected by a pinion to the divider DH3 is thus rotated in accordance with the division of the deflection in the plane of the line of sight by the cosine of the angle of advance eievation. This quantity is algebraically subtracted from the bearing in the differential B23 to the center of which the shaft D22 is connected.

The value of advance range, advance elevation and the advance bearing of the target may be thus obtained on the mechanism disclosed. To obtain the ultimate factors of gun setting certain corrections must be made to these functions. This is the purpose of the remainder of the mechanism.

The total gun elevation E is obtained by adding the super elevation, the vertical deflection due to the movement of the target UT and the observed elevation of the target. The super elevation, obtained in the manner previously described, is added to the vertical deflection due to the movement of the target, as represented by the rotation of the shaft A28, in a differential 213 to obtain the total vertical deflection or sight depression U Connected to the center of the differential D4 to be driven in accordance with shaft e9 is a shaft e14 which is connected to rotate the center of differential e13. Shaft A28 the angular movement of which represents the vertical deflection due to movement of the target is connected to one side of the differential e13. Angular movement of a shaft U1 connected to the other side of the differential e13 therefore represents the total vertical deflection or sight depression.

A follow-up mechanism, designated generally by the character U2, which may be any one of those well known in the art is utilized to drive a shaft U3 in accordance with the rotation of shaft U1. Shaft U3 is connected to one side of a differential U4 in which spot corrections are made to the generated total vertical depression through the medium of a crank handle U5 connected to the center of the differential U4. The other side of the differential U4 is connected to a shaft U6 which drives a shaft U7 connected to a transmitter U8. The shaft U6 also drives a shaft U9 which is connected thereto and to one side of a differential U10 which is thus operated in accordance with the total vertical deflection. The center of the differential is operated in accordance with the present elevation angle through a shaft A38 connected thereto. The other side of the differential is connected to a transmitter E which is thus angularly positioned through an angle representing the total gun elevation.

A complementary error corrector is provided for making correction in the vertical deflection due to movement of the target across the line of sight. A suitable correction for this purpose is obtained by taking the product of the square of the deflection and the sine of the advance angle of elevation. For this purpose there is provided a rotatably mounted face cam D23 having a cam groove therein which varies as the square of the angular input to the cam. A cam follower positioned in the groove in the cam actuates, through a link D24, one side of a multiplier DA. The cam D23 is rotated in accordance with the deflection through a pinion D25 mounted on the shaft D10 and meshing with gear teeth on the periphery of the cam D23. The other part of the multiplier is actuated from a cam fQLIQWE i the groove of a rotatably mounted face cam A41. The groove in the cam A41 is laid out such that the distance from the center represents the sine of the angle by which the cam is rotated. This cam is rotated through a pinion A42 mounted on a shaft A43 connected to the shaft A19. The product obtained from the multiplier is represented by the angular movement of a shaft D25 connected to the multiplier through a gear D26. A shaft D27 is connected to the shaft D25 and the center of the differential A27 in which this correction is added.

The mechanism for providing the fuse setting is similar, with the exception of the shape of the cam, to the mechanisms e and T. It includes a cam Fl that is rotated in accordance with the fuse range which consists of the advance range and the dead time correction. The fuse range is obtained by adding the advance range and the proper proportional factor of the rate of change of advance range. This is done in a differential F2 one side of which is connected to the shaft R25 and the center of which is connected in the proper ratio to the shaft R27 through a shaft R37. The other side of the differential and the shaft F3 connected thereto are thus rotated in accordance with the sum of these factors. The shaft F3 rotates the cam F1 through a shaft F4. A cam follower F5 engages the cam F1 and it is movable longitudinally of the cam F1 by a screw shaft F6 which is connected to shaft A18 for rotation in accordance with advance elevation. An arm P7 of the cam follower receives and is slidable on a rotatabiy mounted polygonal shaft F8 which has mounted thereon a sector gear F9. This sector gear meshes with a pinion F10 mounted on a shaft F11 that is connected to a transmitter F12. Movement of the cam follower due to rotation of the cam thus effects angular movement of the transmitter.

From the foregoing description of the instrument illustrated in the drawings it will be appreciated, by those skilled in the art, that there is provided a much simpler mechanism for obtaining the factors of gun setting than those heretofore made. It will also be obvious that various changes be made by those skilled in the art in the details of the embodiment of the invention disclosed in the drawings and described above within the principie and scope of the invention as expressed in the appended claims.

I claim:

1. In gun-fire control apparatus for generating values representing present and advance positions of a target, the combination of a. variable speed device having a rate member settable in accordance with the rate of change of range and an output the rotation of which represents change of range, a cam mechanism having an input element the movement of which represents range and an output element the movement of which represents time of flight corresponding to the input range, a multiplying mechanism having two input members and an output member the movement of which represents the product of the movements of the input members, means operably connecting one input member to the output element of the cam mechanism, means operably connecting the second input member to the rate member of the variable speed device, present range transmission means, advance range transmission means operably connected to the output of the variable speed device, means for adjusting the advance range transmission means relative to the output of the variable speed device, means operably connecting the advance range transmission means to the input element of the cam mechanism, and means differentially connecting the present range transmission means to the advance range transmission means and to the output of the multiplying mechanism.

2. In gun-fire control apparatus for generating values representing present and advance positions of a target, the combination of a variable speed device having a rate member settable in accordance with the rate of change of range and an output the rotation of which represents change of range, a cam mechanism having an input element the movement of which represents the range and an output element the movement of which represents time of flight corresponding to the input range, a multiplying mechanism having two input members and an output member the movement of which represents the product of the movements of the input members, means operably connecting one input member to the output element of the cam mechanism, means operably connecting the second input member to the rate members of the variable speed device, present range transmission means, advance range transmission means operably connected to the output of the variable speed device, means for adjusting the advance range transmission means relative to the output of the variable speed device, means operably connecting the advance range transmission means to the input element of the cam mechanism, means differentially connecting the present range transmission means to the advance range transmission means and to the output of the multiplying mechanism, a second variable speed device having a rate member settable in accordance with the rate of change of bearing and an output the rotation of which represents change of bearing, a second multiplying mechanism having two input members and an output member the movement of which represents the product of the movements of the input members, means operably connecting one input member of the second multiplying mechanism to the output element of the cam mechanism, means operably connecting the second input member of the second multiplying mechanism to the rate member of the second variable speed device, present bearing transmission means, advance bearing transmission means operably connected to the output of the second variable speed device, means for adjusting the advance bearing transmission means relative to the output of the second variable speed device, and means differentially connecting the present bearing transmission means to the advance bearing transmission means and to the output of the second multiplying mechanism.

3. In gun-fire control apparatus for generating values representing present and advance positions of a target, the combination of a variable speed device having a rate member settable in accordance with the rate of change of range and an output the rotation of which represents change of range, a cam mechanism having an input element the movement of which represents range, a second input element the movement of which represents elevation and an output element the movement of which represents time of flight corresponding to the input range and the input elevation, a multiplying mechanism having two input members and an output member the movement of which represents the product of the movements of the input members, means operably connecting one input member to the output element of the cam mechanism, means operably connecting the second input member to the rate member of the variable speed device, present range transmission means, advance range transmission means operably connected to the output of the variable speed device, means for adjusting the advance range transmission means relative to the output of the variable speed device, means operable connecting the advance range transmission means to the input element of the cam mechanism, means differentially connecting the present range transmission means to the advance range transmission means and to the output of the multiplying mechanism, a second variable speed device having a rate member settable in accordance with the rate of change of elevation and an output the rotation of which represents change of elevation, a second multiplying mechanism having two input members and an output member the movement of which represents the product of the movements of the input members, means operably connecting one input member of the second multiplying mechanism to the output element of the cam mechanism, means operably connecting the second input member of the second multiplying mechanism to the rate member of the second variable speed device, present elevation transmission means, advance elevation transmission means operably connected to the output of the second variable speed device, means for adjusting the advance elevation transmission means relative to the output of the second variable speed device, means differentially connecting the present elevation transmission means to the advance elevation transmission means and to the output of the second multiplying mechanism, and means operably connecting the advance elevation transmission means to the second input element of the cam mechanism.

References Cited in the file of this patent UNITED STATES PATENTS 1,811,688 Gray June 23, 1931 1,827,812 Ford Oct. 20, 1931 2,065,303 Chafee et al. Dec. 22, 1936 

